Johne’s disease is the clinical syndrome of end-stage infection with the bacteria Mycobacterium avium paratuberculosis or 'MAP' for short.
Whilst many infected cows never go on to develop the classic signs of extreme weight loss, infected cows are very likely to have reduced performance and are very likely to shed bacteria in dung and milk. Shedding of bacteria poses a huge infection risk to young animals and therefore segregation of infected cows around calving is an essential step for reducing prevalence.
Milk ELISA tests offer a rapid, cost effective and valuable method of monitoring the herd prevalence of MAP infection, allowing timely and evidence based implementation of control strategies. Individual cow milk ELISA testing allows you to screen cows for antibodies to infection and highlight positive cows (and therefore those likely to be infected) and manage them differently to break the cycle of transmission.
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QMMS categorises the milk MAP ELISA results as follows:
Positive (two ELISA test positives out of the last three tests) - these cows are more likely to be infected and are not re-classified once they are categorised as positive, regardless of any subsequent ELISA test results;
Provisionally positive (the latest milk ELISA test is positive);
Uncertain (antibody test is very close to threshold and/or cows that have previously tested positive but have since tested negative);
Currently negative (all tests negative or previously tested positive once but have subsequently tested negative on three consecutive occasions).
As milk ELISA testing will result in some apparent positive results being ‘false’ positives, particularly in low prevalence herds that test relatively frequently, culling a cow based on one positive test result is not recommended. At least two positive tests should be obtained before making definitive decisions as this will increase the certainty that the cow is infected.
The aim of milk ELISA testing should always be to risk manage those cows that are more likely to be infected and segregate these cows from calving areas and the colostrum pool. In reality this means that any cows that are currently listed as 'positive', 'provisionally positive' or 'uncertain' should be identified and managed differently at drying-off in conjunction with advice from your veterinary surgeon
As with our milk recording and bacteriology services, the MAP ELISA service is backed by Royal College of Veterinary Surgeons Recognised specialist advice, helping with interpretation of results and enabling a unique ‘joined-up’ approach to the control of Johne’s disease in your herd.
The suggested QMMS protocol has a strong evidence-base and outlines our interpretation of the latest research evidence on the application of milk MAP ELISA’s and may therefore change as more research in this area is published. Full integration with on farm software is available in conjunction with SUM-IT Computer Systems. In the absence of compatible on farm software your results will be emailed as .pdf files reporting both your current and historic results.
